This invention relates to a magnetic head for recording information on a magnetic recording medium, to a method of manufacturing the magnetic head, and to a magnetic storage unit using the magnetic head.
A magnetic recording medium is disclosed, for example, in Japanese Unexamined Patent Publication of Tokka: No. Hei 9-138,930 (or JP-A 9-138930). JP-A 9-138930 provides a magnetic recording medium to obtain high magnetic characteristics and to improve adhesion property between a substrate and a base layer. According to JP-A 9-138930, first base layers, second base layers, magnetic layers and lubricant layers are successively formed on a substrate. Among the base layers, the first base layers formed near the substrate have higher specific heat than that of the second base layers deposited far from the substrate. Thereby, the temperature in orientation controlling layers and magnetic layers can be enough raised without increasing the temperature in the inside and surface of the substrate so much. Thereby, adhesion property between the first base layers and the substrate can be improved, which prevents peeling of the first base layers.
The magnetic storage units may be a magnetic disk drive. In the magnetic disk drive, data is written and read by thin film magnetic transducers called “magnetic heads” which are supported over a surface of the magnetic recording medium or disk while it is rotated at a high speed. The magnetic head are supported by a thin cushion of air (an “air bearing”) produced by the disk's high rotational speed.
With miniaturization and large-capacity in the magnetic storage unit, a volume per one bit recorded on the magnetic recording medium drastically becomes small. In the manner which is well known in the art, there is a magnetoresistive (MR) head to detect, as a large read output, a magnetic signal generated from a microscopic bit.
Inasmuch as the MR head is exclusively used for reading, the MR head is used as a merged MR head which employs the MR head and an inductive (ID) head for writing in combination. Such as a merged MR head is disclosed, for example, in U.S. Pat. No. 5,438,747, Japanese Unexamined Patent Publication of Tokkai No. Hei 8-212,512 (or JP-A 8-212512), and Japanese Granted Patent Publication of No. 2,821,456 (or JP-B 2821456) which corresponds to U.S. patent application Ser. No. 09/108,252).
U.S. Pat. No. 5,439,747 provides a merged MR head having vertically aligned sidewalls so as to minimize side-fringing and improve off-track performance. When a magnetic recording disk is rotated, a thin film merged MR head, mounted on a slider, is supported above a surface of the magnetic recording disk by a thin layer of air called an “air bearing”. The merged MR head includes an MR read head and an IR write head. The bottom surface of the slider and the merged MR head are in the plane of an air bearing surface (ABS) of the slider. The MR read head includes a magnetoresistive element MR which is sandwiched between first and second gap layers, the gap layers in turn being sandwiched between first and second shield layers. The first and second gap layers are collectively called a magnetic separation layer. In a merged MR head, the second shield layer of the MR read head also serves as the bottom pole piece for the IR write head. The bottom pole piece is called a first or lower magnetic layer. The IR write head has a pole tip region which is located between the air bearing surface (ABS) and a zero throat level and a yoke or back region which extends back from the zero throat level to and including a back gap. The IR write head includes the bottom pole piece and a top pole piece. The top pole piece is called a second or upper magnetic layer. The bottom pole piece comprises the second shield layer of the MR read head. Each pole piece also has a back layer portion which is located in the back region, the back layer portions of the pole pieces being magnetically connected at the back gap (BG). The bottom pole piece includes a pole tip structure which is located in the pole tip region between the ABS and the zero throat level. This pole tip structure includes a bottom pole tip element and a top pole tip element. The top pole piece includes a pole tip structure which is located in the pole tip region between the ABS and the zero throat level. This pole tip structure includes a top pole tip element. The pole tip elements are integrally formed from second shield of the MR read head. A pole gap layer (G) is sandwiched between the pole tip elements.
JP-A 8-212512 discloses a magnetic head for a high recording density in a high-frequency region. Specifically, JP-A 8-212512 discloses a recording and reproducing separated type head which comprises an inductive (IR) write head, a magnetoresistive (MR) read head, and a shield member for preventing the MR read head from being confused due to a leakage magnetic field. The MR read head comprises a lower shield layer formed on a substrate, a magnetoresistance effect layer, electrodes, and an upper shield layer. The IR write head comprises a lower magnetic layer, a write coil, and an upper magnetic layer.
JP-B 2821456 discloses a merged MR head which comprises a MR read head and an IR write head. The IR write head comprises a lower magnetic layer, an insulating layer formed on the lower magnetic layer, a write coil enclosed with the insulating layer, and an upper magnetic layer formed on the insulating layer. The write coil is a patterned conductive layer. The MR read head comprises a lower shield layer, a gap layer formed on the lower shield layer, a magneto-resistance effect element sandwiched in the gap layer at one end thereof, an upper shield layer formed on the gap layer. The lower magnetic layer is the upper shield layer itself.
Recently, a giant magnetoresistive (GMR) read head is made practicable. The GMR read head uses a GMR effect which is capable of realizing a drastic high output in comparison with the MR read head. The GMR read head generally uses a spin valve effect. The “spin valve effect” is a phenomenon where a variation of resistance corresponds to a cosine between magnetic directions of two adjacent magnetic layers and thereby a large variation of resistance is obtained by a small operational magnetic field. Such a GMR read head using the spin valve effect is disclosed, for example, in Japanese Unexamined Patent Publications of Tokkai No. Hei 10-162,322 (or JP-A 10-162322) and Tokkai No. Hei 11-16,120 (or JP-A 11-16120).
JP-A 10-162322 provides a merged GMR head that realizes simultaneously the magnetizing direction of the magnetization fixing layer of a spin valve element and the magnetic anisotropic direction of a magnetic shield or a recording magnetic pole, and that can secure a stable operation of a magnetoresistence effect (MR) read head part and an indudtive (ID) write head part. The merged GMR head disclosed in JP-A 10-162,322 is equipped with an MR read head part having a reproducing function and an ID write head part recording prescribed information on a magnetic recording medium with a magnetic gap part. An MR element is constituted of a center area and end areas. The center area consists of spin valve elements and senses a media magnetic field. The end areas supply a bias magnetic field and an electric current. The other magnetic pole of the ID write head part is constituted of two kinds of laminated magnetic films having a different degree of saturation magnetization. The saturation magnetization of the magnetic film close to a magnetic gap inside each magnetic film is set to be larger than that of the magnetic film away from the magnetic gap.
JP-A 11-16120 provides a magnetic domain structure which may be optimized even without the execution of the head treatment. JP-A 11-16120 discloses a recording and reproducing separated-type head using a thin film magnetic head. The recording and reproducing separated-type head comprises a reproducing or read head and a recording or write head. The reproducing head comprises a magnetoresistence effect film which is sandwiched between first and second shield layers. In addition, the second shield layer serves as a lower magnetic pole of the recording head. The recording head comprises the lower magnetic pole, a shield layer sandwiching a coil, and an upper magnetic pole. The magnetoresistence effect film is a spin valve film.
The GMR read head is practically used at a high-density recording area having a recording density of 3 gigabits/inch2 or more. At a recording area having a recording density less than 3 gigabits/inch2, it is possible to sufficiently cover by a conventional MR head using magnetic anisotropy. That is, a practically significant GMR read head realizes a high-density recording and reproducing of 3 gigabits/inch2 or more. Accordingly, a magnetic storage apparatus constructed using the GMR head is a high-density recording and reproducing apparatus of 3 gigabits/inch2 or more.
On the other hand, in the ID write head carrying a recording function to a magnetic recording medium, an improvement of a high-density recording performance is always requested with development of the GMR read head. In particularly, a high coercive force to the magnetic recording medium is indispensable to carry out a high-density recording. This is to minimize a transition length of a magnetizing recorded in the magnetic recording medium with improvement of a recording density and to stably hold the magnetizing although a length of the magnetizing per one bit is shortened. For this purpose, development for the ID write head to enlarge a recording magnetic field is energetically advanced so as to record the magnetic recording medium of a high coercive force which is suitable for the high-density recording.
Now, with considerations of convenience and low cost in a manufacturing process of the magnetic head, it is effective that a magnetic material is formed by plating. In the plating, it is possible to obtain a desired pattern by forming a photo-resist frame where a shape of magnetic poles (first and second magnetic layers) is preliminarily bored and by growing a plating layer within the photo-resist frame. The first and the second magnetic layers are called lower and upper magnetic layers, respectively. Inasmuch as this method is convenience and low cost, this method presently becomes a standard manufacturing method of a thin-film magnetic head.
Various thin magnetic films suitable for magnetic layers are already known. By way of example, the above-mentioned JP-A 11-16120 discloses a two-layered film comprising a nickel-iron (NiFe) alloy as an essential element. The two-layered film consists of a first magnetic sub-layer having a high saturation magnetic flux density and a second magnetic sub-layer having a low magnetostriction constant. The first and the second magnetic sub-layers are formed by changing a current density by using a flame plating method on an insulating film.
U.S. Pat. No. 4,661,216 discloses an electoplating bath composition for electroplating a coating of a cobalt-nickel-iron (CoNiFe) alloy with low coercivity, high saturation magnetization (4 πMs), and 0 or slightly negative magnetization (λs) for use in thin film heads for reading and writing. The CoNiFe electroplating bath composition disclosed in U.S. Pat. No. 4,661,216 includes a stress reliving agent such as saccharin.
Japanese Unexamined Patent Publication of Tokkai No. Hei 6-346,202 or JP-A 6-346202 discloses a soft magnetic alloy having high Bs, low Hc,and high μ. According to JP-A 6-346202, essential components of this soft magnetic alloy are constituted of iron (Fe), cobalt (Co), and nickel (Ni). In the formula of FexCoyNiz, the atomic ratio of each element in these essential components is expressed by 0.10≦x≦0.55, 0.20≦y≦0.85, 0.05≦z≦0.35 and x+y+z=1. The soft magnetic alloy is substantially constituted of a face-centered cubic crystal single phase. In the case the peak intensity of the (200) plane and that of the (111) plane in the X-ray analysis are respectively defined as I(200) and I(111), I(200)/I(111)≧0.25 is regulated. Furthermore, the absolute value of the saturation nagnetostrictoin value (λs) is regulated to 5×10−6 or below. In this way, the λs can substantially be regulated to zero even in the compositional range by which high Bs can be obtained.
The above-mentioned JP-B 2821456 also discloses a soft magnetic film suitable for the first and the second magnetic layer. The soft magnetic film is a Co—Ni—Fe plating film formed with a plating bath including no addition agent such as saccharin to obtain a pure film having a sulfur content of 0.1% by weight or less. Such a soft magnetic film has a magnetostrictive constant reduced up to a practical level, an extremely high saturation magnetic flux density (Bs) of 1.9–2.2 T, and an extremely small coercive force of 199 A/M or less. The soft magnetic film is called a high-Bs soft magnetic film.
However, when the first (lower) and the second (upper) magnetic layers are formed using the high-Bs soft magnetic film, problems arise as follows:
{circle around (1)} stripping or peeling occurs in the first and the second magnetic layers;
{circle around (2)} cracks occur in a step cover (SC) film which is a boundary face between first and second insulating layers covering the write coil: and
{circle around (3)} cracks occur in a frame resist on forming the high-Bs soft magnetic film, the plating film grows along the cracks, and then abnormality in shape or shape anomaly occurs in the first and the second magnetic layers.